<template>
  <div>
      <h1>第七题 - 买点书</h1>
      <!-- 目标: 把数据铺设到页面上, 当用户点击买书按钮, 书籍数量增加1, 并且要计算累计的和 -->
      <p>请选择你要购买的书籍</p>
      <ul>
        <li v-for="(item,index) in arr" :key="index">
          {{item.name}}
          <button @click="add(index)">买书</button>
        </li>
      </ul>
      <table border="1" width="500" cellspacing="0">
        <tr>
          <th>序号</th>
          <th>书名</th>
          <th>单价</th>
          <th>数量</th>
          <th>合计</th>
        </tr>
        <tr v-for="(item,index) in arr" :key="index">
          <th>{{index}}</th>
          <th>{{item.name}}</th>
          <th>{{item.price}}</th>
          <th>{{item.count}}</th>
          <th>{{item.price * item.count}}</th>
        </tr>
      </table>
      <p>总价格为: {{ allPrice }}</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      arr: [
        {
          name: "水浒传",
          price: 107,
          count: 0,
        },
        {
          name: "西游记",
          price: 192,
          count: 0,
        },
        {
          name: "三国演义",
          price: 219,
          count: 0,
        },
        {
          name: "红楼梦",
          price: 178,
          count: 0,
        },
      ],
    };
  },
  computed: {
    allPrice() {
      return this.arr.reduce((a, b) => {
        return a += b.price * b.count;
      }, 0);
    },
  },
  methods: {
    add(i){
      this.arr[i].count++
    }
  }
}
</script>

<style>

</style>